Downgrading Spine 4.3 data to 4.2

Aisha

I’m trying to downgrade Spine data created in Spine 4.3 so it can be opened and used in Spine 4.2 (Editor only, no Unity runtime involved).

After exporting JSON from Spine 4.3 and opening it in Spine 4.2, the animation curves and timelines appear correct. However, any animations that use translation/transform constraints become severely distorted when opened in Spine 4.2.

This happens directly inside the Spine 4.2 editor, so it does not seem to be related to any runtime or engine integration.

I assume this is caused by changes to translation/transform constraint behavior or evaluation between Spine 4.2 and 4.3.

Is there any recommended workflow to safely downgrade such data (for example, baking constraint results, alternative constraint setups, or specific export options), or are these constraints simply not backward compatible?

Thank you very much for your help.

Misaki

Aisha Sorry for the inconvenience. Regarding transform constraints, specifically, it has been confirmed that in 4.3-beta, the mix values for unconnected properties are all set to 100 when exported for 4.2, requiring the manual effort of resetting the mix to 0. To address this issue, we have the following issue in our GitHub repository: EsotericSoftware/spine-editor964

Erika

Transform constraints changed significantly between 4.2 and 4.3, so the format changed as well. Given that 4.3 is a beta, and that downgrading a json comes with data loss (this is also signaled when choosing a legacy json export), this is an example of the loss that may occurr.

As a possible way to salvage the work, you could try to delete the constraints before exporting, then recreate them after reimporting them in 4.2.

Aisha

Misaki
I've tried setting all other options in the Transform Constraint after the input to 0, but as shown in the video, the position does not return to the correct place.

Did I make a mistake in any step?

Aisha

I’ve tried setting all other options in the Transform Constraint after the input to 0, but as shown in the video, the position does not return to the correct place.

Did I make a mistake in any step?

Misaki

Aisha Note that in your skeleton's transform constraints, the left-side Local checkbox is enabled. Since this option does not exist in 4.2, you cannot simply convert it. The following thread may be helpful regarding this:
https://esotericsoftware.com/forum/d/29641-4339-beta%E9%AA%A8%E9%AA%BC%E6%97%A0%E6%B3%95%E7%A7%BB%E5%8A%A8bug/10

Aisha

Misaki
I understand now. Does this mean that if I have already completed the setup in version 4.3 with all transform constraints using Local, there is currently no way to restore them correctly when converting back to version 4.2?

Because even if I disable Local in version 4.3, the positions become incorrect as well. I’d like to ask whether this issue is planned to be fixed in the future, or if the only solution is to re-set up all transform constraints again in version 4.2.

Thank you very much for your reply.

Misaki

Aisha Yes, if you've already completed a setup assuming the Local option of the source bone use, unfortunately there will be parts where you'll need to redo the setup.

As mentioned in the linked thread, Spine project files are generally backward compatible, but not forward compatible. Therefore, not all settings can be expected to be restored, especially when using newly added options.